Preparation of 3,5-dinitrobenzotrifluoride compounds

ABSTRACT

3,5-Dinitrobenzotrifluoride compounds are prepared by nitration of the corresponding benzotrifluorides with a mixture of oleum and alkali metal nitrate in which the mixture has an SO3:MNO3 molar ratio of 1.5 to 2.0. Alternatively a portion of the alkali metal nitrate can be replaced by nitric acid, but the molar ratio of SO3 to total nitrate remains the same. The reaction takes place at a temperature of up to about 225*C. in relatively short periods of time.

limited ties Patent Smith et al. Apr. 1%, 1973 [56] References Cited UNITED STATES PATENTS COMPOUNDS 2,257,093 9/1941 Friedrich et a1. ..260/646 Inventors: Robert Smith, Anahelm; Kll'by 3,100,170 8/1963 Levy ..l56/20 A. Salisbury, Santa Ana; Morris A. Leaffer, Palo Alto, all Of Calif. Primary Examiner-Leland A. Sebastian [73] Assignee: United States Borax & Chemical Attorney-James Thornton Corporation, Los Angeles, Calif. 57] ABSTRACT [22] Filed: 1970 3,5-Dinitrobenzotrifluoride compounds are prepared [21] APPL 5 224 by nitration of the corresponding benzotrifluorides with a mixture of oleum and alkali metal nitrate in which the mixture has an SO;,:MNO molar ratio of 1.5 to 2.0. Alternatively a portion of the alkali metal [22] :JSSI ..260/64g6725$g1 nitrate can be replaced y nitric acid, bu the molar E5 'f 20/ ratio of $0 to total nitrate remains the same. The

ie 0 care reaction takes place at a temperature of up to about 225C. in relatively short periods of time.

13 Claims, No Drawings PREPARATION OF 3,5- DHNITROBENZOTRIFLUORIDE COMPOUNDS This invention relates to the production of 3,5-

dinitrobenzotrifluoride compounds which are useful as intermediates for the preparation of herbicidal 5 peratures such as below about 90C. Because of the difficulty in adding the second nitro group to the ring at such low temperatures, long reaction times are generally required such as on the order of several days. Attempts to increase the reaction temperatures and thereby reduce reaction time result in considerable oxidation of the trifluoromethyl group and production of carboxylic acid impurity.

We have found an improved method for nitrating the benzotrofluorides in which substantially higher reaction temperatures can be employed without increasing the amount of carboxylic acid impurity nor evolving copious amounts of unwanted S0 or nitrogen oxide fumes. By employing the procedure of the present invention, relatively short reaction times are used to give good yields of the desired dinitro-substituted products.

Thus, according to the present invention, there is provided the method for producing 3,5- dinitrobenzotrifluorides which comprises reacting a benzotrifluoride compound with a mixture of sulfuric acid having excess S0,, and an alkali metal nitrate in which the SO :MNO molar ratio in the mixture is in the range from about 1.5 to 2.0. Thus, by employing such a nitrating mixture one can use elevated reaction temperatures of up to about 225C. without fuming or substantial oxidation of the benzotrifluoride group.

The sulfuric acid should contain excess S0 and preferably corresponds to about 95-40 weight percent H SO, plus about 5-60 weight percent S0 We prefer that the sulfuric acid be about 20-40 percent oleum.

The alkali metal nitrate is preferably either sodium nitrate or potassium nitrate. It is preferred that the nitrate ion in the nitrating mixture be present in an excess of that required for stoichiometry. Thus, as large as a 10 fold excess of the nitrating agent can be used.

By employing the critical SO :MNO molar ratio of 1.5 to 2.0, undesirable fuming during the reaction is avoided even at up to temperatures of about 225C. When the ratio is below 1.5, oxides of nitrogen evolve and when it is above 2.0, SO is evolved. In a preferred nitrating mixture, a portion of the alkali metal nitrate is replaced by nitric acid, and in this case the SO :(MNO I-lNO molar ratio should also be in the range of 1.5 to 2.0. The ratio of nitric acid to alkali metal nitrate in such mixtures is preferably up to about 5.

The desired 3,S-dinitrobenzotrifluoride product is isolated and purified by conventional procedures. For example, the reaction mixture can be added to a large volume of cold water from which the crystalline product will precipitate. The crude product is isolated such as by filtration and can be purified if necessary by recrystallization.

The following examples are given to illustrate the process of the present invention.

EXAMPLE I To a one liter flask was added 398 g. of H SO -25 percent SO oleum (1.49 moles S0 prepared by combining 275 g. of 30 percent oleum and 133 g. of 15 percent oleum). The contents of the flask were cooled by an ice bath and stirred while 80 g.(0.8 mole) of potassium nitrate was added in several small portions, while maintaining the pot temperature below 80C. To this mixture was then added 20.0 g. (0.093 mole) of 2,4- dichlorobenzotrifluoride dropwise over a 10-minute period while maintaining the pot temperature at C. The resultant mixture was heated to 160C. over a 10- minute period and maintained at this temperature for 0.5 hour. It was then allowed to cool to 100-l20C. and the reaction mixture poured into a 2-liter beaker which was full with cracked ice. The desired product solidified to a pale yellow solid in the cold aqueous solution and was isolated by filtration. After drying, 24.6 g. (86.7 percent yield) of 2,4-dichloro-3,5- dinitrobenzotrifluoride was obtained as a yellow crystalline solid, mp. 7273.5C.

EXAMPLE II The procedure of Example I was repeated except a mixture of 330 g. of H 50 30 percent oleum (representing 1.24 moles of SO 32.3 g. (0.38 mole) of sodium nitrate and 19.6 g. of percent nitric acid (0.28 mole HNO was employed as the nitrating agent for 35.5 g. (0.165 mole) of 2,4- dichlorobenzotrifluoride. The mixture was maintained at C. for 16 hours and then 140C. for an additional hour and the product isolated as described in Example l. A yield of 42.5 g. (84 percent) was obtained.

EXAMPLE Ill To 20 g. of fuming sulfuric acid (30 percent) which was chilled in an ice bath was added 4 g. of potassium nitrate. To this mixture was added 1 g. of 2,4- dichlorobenzotrifluoride and the stirred solution maintained at C. for 15 hours. The reaction mixture was then poured onto ice and extracted with two 25 ml. portions of chloroform. The organic extracts were washed with saturated sodium bicarbonate and then water. The chloroform was then removed by distillation to give 1.22 g. (86 percent yield) of 2,4-dichloro-3,5- dinitrobenzotrifluoride.

EXAMPLE IV 2,4-Dichlorobenzotrifluoride (32.2 g.; 0.15 mole) was nitrated according to the procedure of Example 1 using a mixture of 301 g. of !-l-,,SO 30 percent oleum (1.12 moles S0 and 51 g. (0.6 mole) of sodium nitrate. The reaction mixture was heated at 120C. for 12 hours and the product then isolated according to Example 1 to give 37.6 g. (82 percent yield) of the desired 2,4-dichloro-3 ,5-dinitrobenzotrifluoride.

EXAMPLE V 2,4-Dichlorobenzotrifiuoride (20.2 g.; 0.94 mole) was nitrated according to the procedure of Example 1 using a mixture of 327 g. of H 80, 30 percent oleum (1.22 moles S and 80.5 g. (0.805 mole) of potassium nitrate. The reaction took place at 160C. for 45 minutes to give an 80 percent yield of the desired product.

EXAMPLE VI p-Chlorobenzotrifluoride' (27.0 g.; 0.15 mole) was nitrated according to the procedure of Example ll using a mixture of 272 g. of H SQ, 30 percent 50,, oleum (1.02 moles 80 25.5 g. (0.30 mole) of sodium nitrate and 21 g. of 90% l llNO (0.3 mole HNO The reaction mixture was heated at 100C. for 20 hours to give an 85 percent yield of 4-chloro-3,5-dinitro-benzotrifluoride.

EXAMPLE Vll Benzotrifluoride (14.6 g.; 0.10 mole) was nitrated according to the procedure of Example [I using a mixture of 256g. of H SO30 percent S0 oleum (0.96 mole S0 44.0 g. (0.436 mole) of potassium nitrate and 11.5 g. of 90 percent nitric acid (0.164 mole HNO The mixture was stirred at 120C. for one hour and then poured into about 1500 ml. of ice water. The resultant slurry was extracted with three 200 ml. portions of chloroform. The combined chloroform extracts were washed with water, 5 percent sodium bicarbonate and again with water. After drying over sodium sulfate, the chloroform was evaporated to leave 13 g. 55 percent) of 3,5-dinitrobenzotrifluoride.

The 3,5-dinitrobenzotrifluorides are useful as intermediates for the production of herbicidal benzotrifluoride derivatives. For example, one or more halogen substituents on the aromatic ring can be replaced by substituted amines to give outstanding selective herbicides. The following example illustrates the use of 2,4-dichloro-3,5-dinitrobenzotrifluoride as an intermediate for herbicides.

EXAMPLE Vlll N, N -dimethylene-N N -di-n-propyl-2,4-dinitro-6- trifiuoromethyl-l ,3-phenylenediarnine A heavy walled glass reaction tube of approximately 50 ml. capacity was charged with 7.0 grams (0.023 mole) of 2,4-dichloro-3,5-dinitrobenzotrifluoride, 4.64 grams (0.0458 mole) of di-n-propylamine and 40 ml. of absolute ethanol. The tube was sealed and heated in an oil bath at 9499C. for 98 hours. The cooled reaction mixture was then evaporated to dryness to give an oily residue which was extracted with boiling diethyl ether. The insoluble di-n-propylamine hydrochloride was removed by filtration and washed with additional ether. The combined ether filtrates were evaporated to give an oily orange residue which was dissolved in 100 ml. of absolute ethanol and decolorized with activated charcoal. The ethanol and volatiles were removed by evaporation under reduced pressure to give N,N-di-npropyl-3-chloro-2,6-dinitro-4-trifluoromethylaniline (6.77 grams) as a viscous reddish oil. A solution of 4 grams (0.0108 mole) of N,N-di-n-propyl-3-chloro-2,6- dinitro-4-trifluoromethylaniline and 0.93 grams (0.0216 mole) of ethyleneimine in 50 ml. of absolute ethanol was stirred overnight at 35C. The solvent was removed by evaporation under reduced pressure to give a residue which was extracted with boiling hexane. The hexane extract was evaporated to dryness and the residue dissolved in absolute ethanol. After decolorizing with charcoal, the ethanol and volatiles were removed by evaporation under reduced pressure to give the product as a viscous amber oil, which was identified by its proton nuclear magnetic resonance spectrum.

7 Various changes and modifications of the invention can be made and, to the extent that such variations incorporate the spirit of this invention, they are intended to be included within the scope of the appended claims.

What is claimed is:

l. The method for producing a 3,5- dinitrobenzotrifluoride which comprises reacting a benzotrifluoride compound with a mixture of sulfuric acid having excess and an alkali metal nitrate at a temperature of up to about 225C., said mixture having an SO :MNO molar ratio in the range of about 1.5 to 2.0, in which M represents said alkali metal.

2. The method in accordance with claim 1 in which said mixture also contains nitric acid as a source of nitrate ions and the SO :(MNO HNO molar ratio is in the range of about 1.5 to 2.0.

3. The method in accordance with claim 1 in which said sulfuric acid is 20-40 percent oleum.

4. The method in accordance with claim 1 in which said benzotrifluoride compound is 2,4-

dichlorobenzotrifluoride.

5. The method in accordance with claim 1 in which said benzotrifluoride compound is pchlorobenzotrifluoride.

6. The method in accordance with claim 1 in which said benzotrifluoride compound is benzotrifluoride.

7. The method in accordance with claim 1 in which said reaction temperature is in the range of about 50 to 210C.

8. The method in accordance with claim 1 in which an excess of the stoichiometric amount of nitrate compound is employed.

9. The method for producing a 3,5- dinitrobenzotrifluoride compound which comprises reacting at a temperature of about 50 to 210C. a benzotrifluoride compound with a mixture of 20-40 percent oleum, alkali metal nitrate and nitric acid in which the SO :(MNO HNO molar ratio is about 1.5 to 2.0 and the l-lNO zMNo molar ratio is up to about 5, the mixture of nitrate compounds being present in a stoichiometric excess, said M representing said alkali metal.

10. The method in accordance wite with 9 in which said benzotrifluoride compound is pchlorobenzotrifluoride.

1 1. The method in accordance with claim 9 in which said benzotrifluoride compound is 2,4- dichlorobenzotrifluoride.

12. The method in accordance with claim 9 in which said alkali metal is sodium or potassium.

113. in the method for nitration of a benzotrifluoride compound at an elevated temperature of up to about 225C the improvement which consists of employing a stable nitration composition comprising a mixture of sulfuric acid having excess 80;, and an alkali metal nitrate in which the SO :MNO molar ratio in said mixture is in the range of from about 1.5 to 2.0, wherein M 5 is an alkali metal. 

2. The method in accordance with claim 1 in which said mixture also contains nitric acid as a source of nitrate ions and the SO3:(MNO3 + HNO3) molar ratio is in the range of about 1.5 to 2.0.
 3. The method in accordance with claim 1 in which said sulfuric acid is 20-40 percent oleum.
 4. The method in accordance with claim 1 in which said benzotrifluoride compound is 2,4-dichlorobenzotrifluoride.
 5. The method in accordance with claim 1 in which said benzotrifluoride compound is p-chlorobenzotrifluoride.
 6. The method in accordance with claim 1 in which said benzotrifluoride compound is benzotrifluoride.
 7. The method in accordance with claim 1 in which said reaction temperature is in the range of about 50* to 210*C.
 8. The method in accordance with claim 1 in which an excess of the stoichiometric amount of nitrate compound is employed.
 9. The method for producing a 3,5-dinitrobenzotrifluoride compound which comprises reacting at a temperature of about 50* to 210*C. a benzotrifluoride compound with a mixture of 20-40 percent oleum, alkali metal nitrate and nitric acid in which the SO3:(MNO3 + HNO3) molar ratio is about 1.5 to 2.0 and the HNO3: MNO3 molar ratio is up to about 5, the mixture of nitrate compounds being present in a stoichiometric excess, said M representing said alkali metal.
 10. The method in accordance wite with 9 in which said benzotrifluoride compound is p-chlorobenzotrifluoride.
 11. The method in accordance with claim 9 in which said benzotrifluoride compound is 2,4-dichlorobenzotrifluoride.
 12. The method in accordance with claim 9 in which said alkali metal is sodium or potassium.
 13. In the method for nitration of a benzotrifluoride compound at an elevated temperature of up to about 225*C , the improvement which consists of employing a stable nitration composition comprising a mixture of sulfuric acid having excess SO3 and an alkali metal nitrate in which the SO3:MNO3 molar ratio in said mixture is in the range of from about 1.5 to 2.0, wherein M is an alkali metal. 